Este trabalho analisa os factores determinantes do pagamento de remuneracao variavel aos colaboradores das empresas portuguesas, atraves de uma amostra que se mostrou representativa da realidade empresarial portuguesa, relativa aos anos de 2002 e 2003, abrangendo cerca de 28.600 colaboradores. O estudo faz a distincao sob duas vertentes: a decisao de pagar ou nao remuneracao variavel, e o montante da remuneracao variavel. O trabalho baseia-se na teoria da agencia e na teoria do mercado interno de trabalho. Os resultados apurados confirmam que estas duas realidades se suportam em distintos modelos. As hipoteses em estudo sao testadas recorrendo a diferentes modelos com variavel dependente discreta ou, apesar de continua, limitada no seu dominio, com vista a identificar o conjunto de caracteristicas das empresas e dos colaboradores que explicam o montante e a probabilidade de auferir remuneracao variavel e quais os determinantes das diversas formas de remuneracao e as possiveis interaccoes entre elas. Os resultados mostram que o potencial de promocao e carreira constitui uma alternativa a utilizacao de remuneracao variavel e que a remuneracao variavel e mais utilizada para os niveis hierarquicos mais elevados, na area comercial, em empresas de menor dimensao, em filiais de empresas estrangeiras (embora com montantes mais reduzidos) e para colaboradores com niveis de educacao mais elevados. Os resultados relativos a rendibilidade revelam uma relacao positiva com a probabilidade de existencia de remuneracao variavel, mas apenas quando medida pela realidade contabilistica. No entanto, os montantes de remuneracao variavel sao mais elevados nas empresas com menor rendibilidade.
Abstract Although clonal species are dominant in many habitats, from unicellular organisms to plants and animals, ecological and particularly evolutionary studies on clonal species have been strongly limited by the difficulty in assessing the number, size and longevity of genetic individuals within a population. The development of molecular markers has allowed progress in this area, and although allozymes remain of limited use due to their typically low level of polymorphism, more polymorphic markers have been discovered during the last decades, supplying powerful tools to overcome the problem of clonality assessment. However, population genetics studies on clonal organisms lack a standardized framework to assess clonality, and to adapt conventional data analyses to account for the potential bias due to the possible replication of the same individuals in the sampling. Moreover, existing studies used a variety of indices to describe clonal diversity and structure such that comparison among studies is difficult at best. We emphasize the need for standardizing studies on clonal organisms, and particularly on clonal plants, in order to clarify the way clonality is taken into account in sampling designs and data analysis, and to allow further comparison of results reported in distinct studies. In order to provide a first step towards a standardized framework to address clonality in population studies, we review, on the basis of a thorough revision of the literature on population structure of clonal plants and of a complementary revision on other clonal organisms, the indices and statistics used so far to estimate genotypic or clonal diversity and to describe clonal structure in plants. We examine their advantages and weaknesses as well as various conceptual issues associated with statistical analyses of population genetics data on clonal organisms. We do so by testing them on results from simulations, as well as on two empirical data sets of microsatellites of the seagrasses Posidonia oceanica and Cymodocea nodosa . Finally, we also propose a selection of new indices and methods to estimate clonal diversity and describe clonal structure in a way that should facilitate comparison between future studies on clonal plants, most of which may be of interest for clonal organisms in general.
Given the wealth of new RNA structures and the growing list of RNA functions in biology, it is of great interest to understand the repertoire of RNA folding motifs. The ability to identify new and known motifs within novel RNA structures, to compare tertiary structures with one another and to quantify the characteristics of a given RNA motif are major goals in the field of RNA research; however, there are few systematic ways to address these issues. Using a novel approach for visualizing and mathematically describing macromolecular structures, we have developed a means to quantitatively describe RNA molecules in order to rapidly analyze, compare and explore their features. This approach builds on the alternative eta,theta convention for describing RNA torsion angles and is executed using a new program called PRIMOS. Applying this methodology, we have successfully identified major regions of conformational change in the 50S and 30S ribosomal subunits, we have developed a means to search the database of RNA structures for the prevalence of known motifs and we have classified and identified new motifs. These applications illustrate the powerful capabilities of our new RNA structural convention, and they suggest future adaptations with important implications for bioinformatics and structural genomics.
The implications of differences in plant size for seagrass productivlty were examined based on an extensive compilation of data on architecture and growth of seagrass species.The analysis revealed strong allometric relationships between the size of different components, particularly a close scaling of the size of leaves, shoots, and fruits to rhizome diameter, as well as strong relationships between shoot size and the dynamics (e.g turnover rate, plastochrone interval, and longevity) of seagrass leaves and rhizomes of different species.The decrease in rhizome elongation rates and leaf turnover rates with increasing seagrass size demonstrates the importance of architecture for seagrass productivlty, and also provides explanations for the different ecological roles of small, colonizing species, and large, climax seagrass species.In addition, these results demonstrate that while habitat conditions have important Influences on seagrass productivity, differences in size may explain the vast range of turnover tlmes, plastochrone intervals, and module longevities, encountered among seagrass species.
